Computer technology has evolved at an amazing rate in the past few decades. Further increases in the density of semiconductor integrated circuits may soon end due to the practical difficulties in patterning features with dimensions smaller than the wave length of ultraviolet light and soft x-rays. Ultimately, features cannot possibly be smaller than the length scale of single atoms and molecules.
At the molecular level, quantum effects may provided huge advantages as well as problems not encountered at larger dimensions. Quantum computing has recently emerged as a possible approach to developing smaller computing devices that operate on the atomic level. In general, a traditional computer encodes information in a series of bits for computation that are manipulated via Boolean logic, which is based on binary mathematics. For example, a 32-bit digital computer generally manipulates one or several 32-bit operands during execution of a single instruction. A single instruction generally produces one or several 32-bit result values, each representing one of 232 different possible result values. Thus, a single instruction maps one or several operands to one or several results, each within a range of 232 values. On the other hand, a typical quantum computer utilizes the +½ and −½ nuclear spin states for isotopes such as 13C and 19F to represent the Boolean logic one and zero. In addition, the nuclear spin is also a quantum mechanical object that can exist in a superposition of +½ and −½ nuclear spin states. In theory, a typical 32-quantum-bit quantum computer can produce any combination of 232 values (i.e., 232! combintations) as a result of executing an instruction, providing for massive parallelism. However, in order to take advantage of the inherent ½-spin state of isotaopes such as 13C and 19F, the processor must be operated at temperatures near absolute zero.
Computer manufacturers, engineers, and physicists have recognized the need for quantum computers that can handle the increasing demand for speed and computational volume and that are capable of operating at room temperature.